The study objective was to investigate the influence of microbiologically obtained surfactin on the feeding and development of Oulema melanopus and Oulema gallaeciana on spring wheat ( Triticum aestivum) and spring barley ( Hordeum vulgare). The purified bioproduct was applied to the leaves of cereal plants at a concentration of 660.5 mg · l ^–1. The tests were conducted as a no-choice test and a choice test. Pest feeding and egg-laying were analyzed. The addition of surfactin to the food reduced the feeding of female and male tested insects as compared to controls. Male pests caused less damage to plants than females. Insect feeding on surfactin-treated plants was low in the first days of the experiment. The tested insects laid fewer eggs on plants treated with the biosurfactant. In terms of food selection, both female and male Oulema spp. were much more likely to choose food to which surfactin had not been applied. It can thus be concluded that surfactin can contribute positively to the biological control of beetles of the genus Oulema under natural conditions. However, further research is needed to better understand the mechanisms by which analogues of this compound limit the development of this cereal pest in its natural environment.